The present invention relates to a high-speed tape transport system in a magnetic reproducing apparatus and more particularly to a system which controls the rotation of a reel motor for a reel so that the speed of the high-speed travel of a magnetic tape traveling by being taken up on that reel in an apparatus for magnetic recording/reproducing of video signals becomes constant.
Heretofore, in an apparatus for magnetically recording and reproducing video signals on a magnetic tape (hereinafter referened to as VTR), there has been a system which, as it causes the magnetic tape to travel in the forward direction or the reverse direction at a high speed of the order of 10 times the traveling speed at the time of normal recording or reproducing, reproduces the recorded signals, and, as the operator observes the high-speed reproduced picture, a desired recording position on the magnetic tape is sought out in a short time, that is, a system for carrying out a so-called high-speed search reproduction.
For feeding the magnetic tape at high speed in order to accomplish this high-speed search reproduction, there has been a method in which the capstan is rotated at a high speed of approximately 10 times that during ordinary recording and reproducing, and the magnetic tape is driven by this capstan to travel at the high speed. In addition, there has been a method in which the reel on the side taking up the magnetic tape (i.e., the take-up reel at the time of forward travel and the supply reel at the time of reverse travel) is caused to rotate at high speed.
However, by the former method in which the magnetic tape is driven to travel at high speed by rotating the capstan at high speed, since the capstan is rotated at a high speed of approximately 10 times its speed at the time or ordinary recording and reproducing, a voltage which is greatly higher than the applied voltage at the time of ordinary recording and reproducing must be applied to the capstan motor. For this reason, a great load is imposed on the capstan motor, which is thereby used under an unreasonably severe condition, whereby the serviceable life of the capstan motor is shortened. This has been a problem in the prior art.
Furthermore, there has also been a method in which, by the use of a speed-changing mechanism employing gears, rotational output of a great speed variation range is obtained without changing the rotation of the capstan to a great extent. This method, however, has been accompanied by problems such as increase in the cost of the apparatus and in the required space for installation due to the use of the speed-change mechanism and, moreover, instability of the tape travel which gives rise to wow and flutter.
On the other hand, by the latter known method in which the reels are rotated at high speed, a constant driving voltage has been applied to the reel motor for driving the winding-up reel. For this reason, as the magnetic tape travels and is taken up on the reel, the diameter of the roll of the magnetic tape already wound around the reel varies. As a consequence, the load on the reel motor changes, whereby the traveling speed of the magnetic tape is not constant. Consequently, satisfactory search reproduction cannot be carried out. For example, in the case where a reproduced signal is a color video signal, degradation of color is caused in the reproduced picture by time base fluctuation which cannot be corrected by the chrominance signal processing circuit of the reproducing system.